The invention relates to systems for probing test objects and automatically monitoring the probe position of the object, such as in non-destructive testing (NDT) of structures in which an electrical test signal is produced representing some characteristic of the object, and variations in the test signal are correlated with different probe positions.
While the invention has a broad range of applications, it is particularly useful in the NDT field. Often in nondestructive testing, there is a need to provide a record of probed-for test signals as a function of probe position. For example, in ultrasonic NDT systems, an ultrasonic transducer probe is mounted on a mechanical linkage that allows the probe to be movable in a constrained pattern over a test structure. Position transducers are associated with the mechanical linkage and produce electrical signals representing the instantaneous position of the probe in relation to the test structure. The ultrasonic transducer in the probe produces variable test signals related to a particular characteristic of the test structure and such signal variations can be recorded as a function of the probe position signals.
However, the mechanical linkage that is commonly used to generate the probe position signals has a number of drawbacks, especially in certain test environments. For example, when the test structure and the inspection area thereon are relatively large, mechanical linkage systems lack the flexibility and scale needed to scan large areas. The testing of aircraft skins is one example of a test environment presenting the above-noted difficulties. The orientation and relatively large surface expanse of test areas on the aircraft skin are generally incompatible with the use of mechanical linkage assemblies. Also, the lack of portability of most mechanical linkage systems, particularly in systems that are capable of testing a relatively large surface area, is a further shortcoming.
The inherent nature of mechanical linkage, particularly when constructed to span relatively large test areas, has severe practical limitations in providing a suitably high level of position resolution. When an NDT probe is connected to the mechanical linkage, often unwanted constraints result, limiting the operator's independent control over movement of the probe from position to position.
Additionally, existing NDT systems of this general type do not provide an effective presentation of the probed-for test data. As a result, the data developed by such systems are difficult to analyze, increasing the possibility of the operator overlooking significant structural faults.
Accordingly, it is an object of the invention to provide in a method and apparatus of the above-described type, improvements that are characterized by an overall greater flexibility and ease in independently positioning and moving the probe, while still developing data representing the probe signal as a function as probe position. Related objects include system portability, enhanced resolution and self-referencing of the monitored probe position.
Another object of the invention is to provide a correlated probe signal and probe position method and apparatus having the above-characterized capabilities and further providing that the probe NDT signal and probe position data are correlated and displayed in a manner that facilitates rapid assimilation and interpretation of the test results.